The present invention is directed to improved polymerizable acrylate and/or methacrylate based adhesive compositions, well suited for bonding typical plastic components, and especially well suited for the bonding of the so-called "difficult to bond" plastics (e.g., chemical-, environmental-, and solvent-resistant plastics) and like components.
Traditionally, the adhesive bonding of plastics has been a difficult task, requiring either a great deal of surface preparation and/or the use of highly specialized adhesive formulations. Such methods and compositions are described in U.S. Pat. Nos. 4,397,707 to Dawdy, 4,200,480 to Wolinski et al., 3,987,122 to Bartz et al., 3,962,498 to Owston, and 3,873,640 to Owston et al.
Polymerizable acrylate and/or methacrylate based adhesives generally exhibit good adhesion on unprimed non-crystalline thermoplastic materials. It is believed that this good adhesion results because the base monomer (such as methyl methacrylate) can solvate the plastic prior to hardening to provide the needed "bite" for strong bonds.
Many advanced thermoplastic materials that are either currently being used or have been considered for automotive structural applications are designed or have been modified for enhanced heat resistance, dimensional stability, environmental durability and chemical resistance (e.g., to gasoline, detergents, etc). Such designs and modifications often make these plastics inherently difficult to bond through the solvating effect which occurs with typical acrylate or methacrylate based adhesives.
Specifically, polyurethane and epoxy adhesives normally used in automotive bonding applications bond many of these materials only with the use of extensive pretreatment, if at all. Both of these adhesive classes require long cure times at ambient temperature and/or exposure to elevated temperatures to effect even handling strength. Systems designed for faster development of strength often have extremely short and impractical working life.
Thus, some alternative method of providing the necessary anchoring capability on the bonding surfaces of difficult plastic materials is necessary.
The present invention thus provides economical adhesive agents which provide surprisingly effective bonding for components which include solvent-resistant plastics and like materials.
In addition, the adhesive agents of the present invention either improve or maintain the ability to bond conventional plastic materials in comparison with conventional adhesives of this type.